The fluorescent detection of cancer with a photoactivated drug, Photofrin (R) II, and blue light (e.g. 410 nm) has been demonstrated to be a sensitive endoscopic method for locating both tumors and early stages of cancer not readily detectable by other techniques. Although the method shows promise of being able to improve the accuracy of biopsy techniques, the current instrumentation for fluorescence excitation and detection requires lasers and electronics too costly for widespread use. Consequently, fluorescence-guided biopsy techniques cannot be applied on a routine basis simply as an aid to identifying malignant tissue. The objective of this proposal is to develop a low cost instrumentation package that can be used with a biopsy forceps, either in a rigid or flexible endoscope, to aid the physician in distinguishing between malignant and normal tissue during endoscopic examinations. The proposed method involves a non-laser, excitation light source and ratio fluorometry with bandpass filters and photodiodes for detection. The goal of phase I is proof of principle for the method using a xenon arc lamp-based, fiber optic light source and previously reported methods of detection; in phase II, an engineering prototype would be developed in which the sophisticated detection equipment of phase I would be replaced with appropriate photodiodes and simple data reduction electronics. Experiments on an animal model will compare the accuracy of the technique to previous experiments performed at Cedars Sinai Medical Center.